1. Field of the Invention
The present invention relates to a power supply circuit for electric devices provided with a stand-by power supply circuit and a main power supply circuit in an electric device, in which the stand-by power supply circuit and the main power supply circuit can be controlled based on the remote controller operation so that the power consumption of the electric device during stand-by status can be reduced approximately to zero.
2. Description of the Related Art
Some conventional electric devices such as TV sets are designed to supply the power fed from the commercial AC power source to the stand-by power supply circuit and, at the same time, to the main power supply circuit via the stand-by switch. Such an electric device usually supplies the power to the stand-by power supply circuit to make at least the control means operable so that it can be controlled by the remote controller (stand-by status). To actually operate the main circuit of the device, the user operates the power key on the remote controller to turn on the stand-by switch, which turns on the main power supply circuit to lead the above main circuit to the operation status.
FIG. 6 shows the configuration of a power supply circuit used in a conventional electric device.
In FIG. 6, commercial AC power source 1 is connected via a relay 3 to a rectifier smoothing circuit 4 and further connected to input terminals 5 and 5' of a main power supply circuit 2 which operates various load circuits (main circuit) of a main unit 20. The relay 3 consists of a drive winding 3A, a relay switch 3B and a drive circuit 3C. The rectifier smoothing circuit 4 has a full-wave rectifier circuit 401 and a smoothing capacitor 402. The main power supply circuit 2 comprises, for example, a switching type regulated power supply circuit. With the relay 3 turned on at the time of the activation of the device, the DC voltage from the rectifier smoothing circuit 4 is supplied to the main power supply circuit 2 and the main power supply circuit 2 generates various sizes of regulated DC voltage, so that the generated DC voltage is supplied from output terminals 51, 52 and 53 to various load circuits (main circuit) not shown.
The commercial AC power source 1 is also connected to input terminals 7 and 7' on the primary side of a stand-by power supply circuit 6. Connected to output terminals 8 and 8' on the secondary side of the stand-by power supply circuit 6 are the load circuits required for stand-by operation, which are a microcomputer 9 for control, a light receiver 10 for the remote control signal and the drive circuit 3C of the relay 3. The load power is supplied to these sections in the stand-by and ordinary operations. The above stand-by power supply circuit 6 comprises, for example, a switching type power supply circuit having a rectifier smoothing circuit 61, a switching device 62, a converter transformer 63 for voltage conversion and a rectifier circuit 64 on the secondary side of the transformer.
To the light receiver 10, the infrared remote control signal is input from a remote controller 11. The remote controller 11 comprises a microcomputer 111 for control, a key matrix 112 including a power key and an infrared light generator 113 and is designed so that, when a certain key is pressed, the infrared code signal corresponding to the key is transmitted.
In the power supply circuit having the configuration above, the stand-by status can be switched to the ordinary operation status as described below. When the user presses the power key on the remote controller 11, the remote controller 11 transmits the infrared code signal to the light receiver 10 of the main unit 20 and, this code signal is transmitted to the microcomputer 9 of the main unit 20, and then the microcomputer 9 transmits the main power supply ON/OFF signal to the drive circuit 3C of the relay 3. Alternatively, in the circuit configuration without a relay 3, the main power supply ON/OFF signal is transmitted to the main power supply circuit 2 for switching to the operation status.
Conventionally, the electric device in stand-by status needs to always have the power supplied to the load circuits (such as the microcomputer 9 and the light receiver 10) required for stand-by operation because it receives the infrared signal transmitted from the remote controller 11 and operates the main power supply circuit 2 of the main unit 20. The required power is supplied from the commercial AC power source 1 via the stand-by power supply circuit 6. The device in the stand-by status consumes the power though the consumption level is quite lower than that in the ordinary operation status. Even while the user does not actually use the device, the device keeps on consuming the power. The power consumption in a year would be increased due to such consumption.
As described above, the conventional power supply circuit uses the commercial AC power source as the power source for the stand-by power supply circuit and, in the stand-by status, its power consumption from the commercial AC power source is increased.